Capybaras (Hydrochoerus spp.) Fact Sheet: Behavior & Ecology

• Rest close together at water's edge in morning
• Rest in water or mud during the heat of the day
• Most grazing in late afternoon and evening; graze in short sessions at night
• After disturbances from humans, more nocturnal and shy
• Group size fluctuates with wet/dry seasons

Territory Size

• Territories remain very stable for several years
• Along rivers, groups space themselves from 100 to 500 m (.06 to .3 mi.) apart
• Groups may occupy a home range from 2 to 200 hectares (4.9 to 494 acres)
• Average group uses 5 to 20 hectares (12.4 to 49.4 acres)
• In one study, each group used a home range averaging about 79 hectares and defended a territory of 9 hectares
• Density of capybara within their territories quite high compared to other tropical herbivores of similar size
  • Biomass of capybara 10 times greater than similar sized grazing Bohr's reedbucks' biomass
  • Density of capybara populations reflects high primary productivity of savanna habitats in Llanos of Venezuela

General

• Social animals living in groups
  • Dry season: up to 100 individual at water sources
  • Wet season: group size up to 40 individuals
• Bonds between animals maintained by touching, grooming, scent marking, vocalizations
• High levels of sociality possibly a response to risk of predation and resource availability
  • Capybara similar in this trait to South American desert and rock cavies and maras

Hierarchy

• Herds with dominant and subordinate males plus females and young
• Typical make-up of breeding groups: one male and 4-14 females
• Dominance positions very stable, lasting for years
  • Dominant male may claim access to best water holes, parasite-eating birds, and females in estrus
  • Largest males are usually dominant individuals
  • Size not a factor in status among subordinate males
  • Subordinate males tend to occupy positions on edges of resting groups, away from dominant male
• No bachelor groups
  • Males not in groups have little protection from predators
  • Outside the group, no chance for reproduction

Groups defend territories

• Exception to this rule: quick unchallenged passage by neighboring capybara to reach distant territory
• Capybara bark at intruders; then if necessary, jump in river or run away

Scent-mark using anal glands

• Performed by both sexes
  
• May play a role in defining territories

Aggression

• Male aggression more frequent with increasing numbers of males in group
• Harassment and chasing = main form of male/male aggression
  • Subordinate males rarely retaliate
  • Retaliation involves facing opponent, both animals rushing towards each other, rearing on hind legs, grappling, loser fleeing
  • Subordinate males often suffer serious bites to rump as they flee
  • Most commonly, dominant male walks, nudges, or "escorts" subordinate male to edge of group
• Grooming lessens tension between individuals and removes parasites

Play

• Young in groups play in water, imitate males
• Like other cavy-like social rodents, individuals chase each other, play-wrestle, gallop

Visual Signals

• Greatly enlarged scent glands on top of snout in male signals status and may attract females
• Size of male's morrillo is a sign of rank

Vocalization

• Infants and young constantly emit a guttural purr, perhaps to stay in touch with group; losers in aggressive matches also make this sound in appeasement
• Low clicking sounds of contentment
• Sharp prolonged whistles, squeals, short grunts
• Alarm bark or cough
• Most warning calls come from subordinate males in a group; companions react by standing alert or plunging into nearest water
• Females emit a whistle when in estrus
• Males tooth-chatter as sign of aggression
• Many other closely related species also highly vocal, especially guinea pigs and cavies
• Capybara audio provided by BBC
  
  

Olfaction/Scent Marking

• Amount of scent-marking correlates with dominance rank 
• Both sexes scent mark with anal gland; females less frequently
• Group members may recognize each other by their unique mix of scent chemicals

• Excellent swimmer; good diver, can stay underwater for up to 5 minutes
• Move from place to place in short bursts of travel not more than 200 m. (.12 mi.) with long rests between
• Walks, grazing, in typical day about 700 m (.43 mi)
• Star-shaped footprints
• Rather sedentary habits allow ranchers to manage capybara without fences
• Several juveniles may ride on female's back, as she swims

• Predators: puma, jaguar, wild dogs, humans
• Juveniles preyed upon by foxes, ocelots, cayman, raptors, occasional possums (attacking infants), anaconda
• When attacked by wild dogs, capybara group forms defensive huddle with young in center, adults facing outwards
• Co-exist with domestic cattle
• At least nine species of birds increase their feeding rate by associating with capybara
• Especially jacana, scarlet ibis, sharp-tailed Ibis, white Ibis, buff-necked ibis, swifts
• Egrets hunt from moving and stationary capybara's backs
• Swifts hunt low overhead or from capybara's head
• Researcher observed capybara soliciting tick-eating (Amblyomma spp.) by yellow-headed caracara
• Five bird species associated with capybara in order to find food. (Tomazzoni et al 2005)
• Southern caracara, rufous hornero, cattle tyrant, yellow-headed caracara, shiny cowbird
• Strategies of the birds included using the capybara as a perch, walking with the capybara to catch flushed prey, foraging in capybara skin

Image credit: © San Diego Zoo Wildlife Alliance. All rights reserved.

Lord-Rexford (1994)
Herrera & Macdonald (1989, 1993)
Macdonald (1981a, b)
Nowak (1999)
Ojasti (1991)
Rowe and Honeycutt (2002)
Tomazzoni et al (2005)